Hemostatic agents and tissue sealants are routinely used to prevent excess blood loss and to reconstruct tissue during surgical repair. Fibrin glue was approved by the FDA in the 1990's and can be used to impart topical hemostasis, provide sealant properties that are suitable is some clinical applications, and promote tissue approximation. Fibrin glue mimics the final steps of the coagulation cascade. In the presence of thrombin, fibrinogen is converted to fibrin. Thrombin also activates Factor XIII, which stabilizes the clot, by promoting polymerization and/or cross-linking of the fibrin chains to form long fibrin strands. This process usually occurs in the presence of calcium ions. It proceeds independently from the remainder of the coagulation cascade, and provides some degree of hemostasis even with defects in other portions of this pathway. There is subsequent proliferation of fibroblasts and formation of granulation tissue within hours of clot polymerization. The fibrin clot caused by the sealant degrades physiologically. Fibrin sealant can be manufactured from pooled or single source donors.
The composition of fibrin glue products varies, but they generally include a 2-vial system containing fibrinogen, thrombin, factor XIII, and calcium (typically calcium chloride). Fibrin glue products generally include a first component including fibrinogen and Factor XIII (analogous to the “resin” portion of a two part epoxy kit) and a second component including thrombin in a CaCl2 solution (analogous to the “catalyst” component of an epoxy kit). The components may be applied sequentially or simultaneously to the repair site, for example, using a double-barrel syringe onto a dry tissue bed. Prior to polymerization, the fibrin sealants acts as a flowable, sprayable “sticky” liquid that is designed to adhere to wet surfaces. Once polymerized in situ by the addition of thrombin and calcium it becomes a semi-rigid, hemostatic mass intended to hold tissue or materials in a desired configuration. Preparation takes approximately 15 minutes and once the components have been mixed, the product is available for use for 4 hours before the thrombin degrades. Used within their limitations, tissue sealants offer clinicians a valuable and versatile tool for the treatment of bleeding.
However, currently available tissue sealants generally do not perform well in wet or “bleeding” applications. Current commercially available tissue sealants and hemostatic agents are generally either too slow, too cumbersome, lack optimum adhesive properties, or lack the tensile strength required for suturing and preventing arterial blood loss. In addition, many currently available sealants do not have the mechanical strength to address many clinical wound closure demands. Accordingly, a tissue patch that addresses each of these shortcomings would be desirable.